Positive displacement variable volume delivery pump and associated control system



SePt- 17 1957 L. E. osBoRNE 2,806,430

POSITIVE DISPLACEMENT VARIABLE VOLUME DELIVERY PUMP AND ASSOCIATEDCONTROL SYSTEM 2 Sheets-Sheet l Filed March 22. 1952 Sept. 17, 1957 L.E, OSBORNE 2,806,430

' POSITIVE DISPLACEMENT VARIAB VOLUME DELIVERY PUMP AND ASSOCIATED COOL'SYSTEM Filed llarch 22, 1952 2 Sheets-Sheet 2 l-Illl 42 m "j 45 5J 1NV EN TOR.

2,805,430 Patented Sept. 17, 1957 ein POSITIVE DISPLACEMENT VARIABLEVOLUME DELIVERY PUMP AND ASSOCIATED CONTROL SYSTEM Lyle E. Osborne,South Bend, Ind., assistanttn Bendix Aviation Corporation, South Bend,Ind.` corporation of Delaware Application March 22, 1952, Serial No. 278.61m

11 Claims. (Cl. 10S- 37) This invention is concerned with pumpingsystems ci that type utilizing a positive displacement pump having meansfor varying the output or pump delivery at constant stroke, thusavoiding the problems which arise in connection with pumps whereindelivery is varied, for example, by varying the effective angle of awobble plate.

An object of the invention is to provide a pumping system of the typespecified having the advantages of relative simplicity in constructionand reliability in operation.

Another object is to provide a combined positive displacement andby-pass pump and associated control for fuel supply systems for engines,particularly gas turbine or jet engines, wherein a wide range oimetering pressures is available or may be selected and maintained with aminimum amount of fuel by-passed back to the low presa sure side of thepump.

Another object is to provide a positive displacement pump and associatedcontrol system wherein a relatively wide range ot' delivery pressuresare available with n minimum of temperature rise created in the pumpedfluid due to heat energy absorbed by the iiuid.

Another object is to provide a system of the` type specified having aquick time response to changes in demands on the system.

Another object is to provide in a pumpingy system of thc type specifiedmeans for avoiding surge when the pump responds to a change in demandfrom an engine t'ucl control or analogous device.

Another object is to provide a combined check valve and control valvearrangement for reciprocating plunger or like positive displacementpumps which permits varying of the pump output at constant stroke and atthe same time tends toward simplicity in construction and operation.

A further object is to provide an improved fue! pressurizing and controlsystem particularly gas turbine engines.

A still further object is to provide in a wobble plate, reciprocatingplunger type pump improved means for avoiding side thrust on theplungcrs.

The foregoing and other objects and advantages will become apparent inview of the ioilowing description taken in conjunction with the drawingswherein:

Figure l is a view in sectional schematic of a pump and associatedcontrol system in accordance with the invention;

Figure 2 is an enlarged view in section of one of th.: check valves andadjacent parts; and

Figure 3 is a cross section view taken substantially' on the line 3 3 ofthe Figure l.

Referring to the drawings, a main exterior pump body or housing isgenerally indicated at 161; it consists of a hollow cylindrical member'l0', defining a pump chamber 11 and having a bolting-on liange l2 at oneend thereof, to which is attached another cylindrical section 13, thelatter in turn having a bolting-on flange 14 for attachment of end plate15.

The section 13 is provided with a series of bores 16, arranged inannular formation, and in each ot said bores iS Secured a plungerbushing i7. A series of pumping adapted fer i plungers 18 are mounted toreciprocate in the bushings 17; they are shown as being of hollowcylindrical form, each having a tappet or bearing shoe 19 secured in theouter open end thereof.

The chamber 11 receives the lluid to bc pumped, fuel in the presentinstance, which is conducted thereto by way of a conduit 2l) andentrance passage 20 formed in a hollow boss 21 and retainer 22. Apumping chamber 23 is defined in cach hollow bushing 17 at the inner endof cach plunger, and when the plunger is retracted, fuel flows to thcchamber 23 by way of passages or ports 24, formed in the annular walls25 defining the bores 16 and in the bushing itself, note lowerright-hand portieri of Figure l where one of the plungers is shown inretracted position. Springs 26 are provided to retract the plungers,said springs at their outer ends engaging retainers 27 and at theirinner ends abutting the annular walls or bushing sockets 25.

A series of check valves, one for each plunger 1S and pumping chamber23, are indicated at 28; they are each mounted to slide in guidebushings 29, the latter being located in a series of bores 30, formed inthe housing section 13, and held in place by hollow cnd nuts 3l. Theinner or left-hand end of each bushing 29 defines thc adjacent end wallof thc pumping chamber 23, and it also defines a seat 32 for the saidvalve; and when the lutter is unscatcd, fuel may pass through dischargeport 33, chamber 34, ports 34', annular chamber 35 and thence by way ofports 36 to a common central chamber or manifold 37, the latter being incommunication with outlet passage 38 and delivery conduit 39.

Each check valve 28 is hollow, defining chamber 40 for mounting a spring41, which exerts a force on the valve tending to seat the same. ln orderto provide a controllable fuel differential across each valve. thelatter is mounted to permit a certain leakage ot fuel from the highpressure side to the low pressure side thereof, or from the chamber 34to chamber 40. This may be done by a predetermined clearance ortolerance between the valvc and its bushing, or by a series ofcalibrated vent holes provided in the wall of the valve, as at 42, or bya suitable bleed (not shown) between common central chamber 37 andmanifold 44. This leakage or pump control fuel in chamber 4l) flowsthrough ports 43 in the end nuts 31 to annular chamber or manifold 44,common to all the checit valve chambers 4t), from which it may flow byway of passage and conduit 46 to a control unit to be described.

A wobble plate assembly is generally indicated at 47; it comprises awobble plate proper 47', having a hub which is keyed or splined to adrive shaft 48, said plate being formed with bearing surfaces 49 and49'. A socalled torque block is indicated at 50; it is formed with aninner convex clearance surface, which permits a wobbling or rockingmotion with respect to the shaft 48. Two opposite sides of this blockare inserted between the fingers 51, 5l of a yoke which projectsrearwardly from thc hub of a thrust plate 52, which at its outer edge isformed with a flange 52'. A bearing ring S2 is secured to the thrustplate and is contoured to engage the bearing surfaces 49 and 49 of thewobble plate 47. The block 53 and consequently the thrust plate 52 areheld against rotation by the opposed fingers 53, 53 of a yoke whichprojects forwardly from the rear end section 13 of the pump body 10 `andspans the two opposite sides of the block which lie at right tangles tothe sides spanned by the fingers 51, 51', see Figure 3. To facilitateassembly, screws 53 may be threaded through the fingers 53, 53' intoopenings formed in the adjacent sides of the block 50, to hold thelatter in place between said lingers. 0bviously, once the block isengaged between all four of the yoke lingers, a connection isestablished between the thrust plate S2 and the pump housing which holdsthe thrust plate against rotation while permitting nutation or awobbling motion thereof.

The outer edge portion of the thrust plate 52 has threaded therein aseries of plunger-engaging shoes or contact members S4, one for eachplunger 18, each of the shoes S4 being provided with a cone-shapedbearing sur face 54. The purpose of the particular bearing surfacearrangement of the shoes 54 is to provide `a straight line thrust on theplungers at all positions of the wobble plate 47' or to avoid sidethrust effects on the plungers.

It will be seen that when the drive shaft 48 is rotated, it in turnimparts rotation to the wobble plate 47. The rotary' action of thewobble plate 47 is converted into axial or reciprocating motion as itCams on the bearing ring 52", to thereby effect reciprocation of theplungers 18. Since the bearing surfaces 54' of the shoes El are taperedor relieved in planes which are always normal to the line of thrustbetween the cam plate 47' land the plungers 18 irrespective of wobbleplate position, the effective thrust on said plungers will always be inan axial direction.

When the pump is in operation, the reaction of the plungers tends toturn the thrust plate 52. This would throw the conical bearing surfaces54 out of alignment with the plunger heads or ends were it not for thetorque block 50, which constitutes a hub for the thrust plate and holdsthe latter against rotation while permitting universal movement aboutthe drive shaft.

To minimize agitation of the fuel flowing into the chamber 1l. a shield55 is attached to the outer exposed surface of the wobble plate 47.

The outer end of the drive shaft 48 is formed with an enlarged hollowannular portion which is journaled in a wobble plate hearing assembly56, 56 and 56"; and beyond this the said shaft is formed with a relievedportion which rotates in an outer removable sealing assembly 57. A stubshaft 48 is inserted in and keyed to the hollow outer extremity of shaft48 and has a drive spline 4S on the outer end thereof.

The bearing assembly for the wobble plate is self-align ing. viz., itwill automatically provide a flush thrust bearing or surface for thewobble plate even though there muy be some misnlignment between thcshaft 48 and bearing and wobble plate assembly. This is due to theeoncavo-convex bearing surfaces provided by the dish-shaped bushing 56and the interitting convex or sphericalashaped floating member 56',which may be made of suitable wearresistsnt metal or other material andhas a certain amount of peripheral clearance to facilitate aligningmovement. Between the member 56' and the adjacent surface of the wobbleplate is a thrust ring 56".

ln the installation as illustrated in the present instance, the improvedpumping and control system is used to supply fuel under pressure to agas turbine or jet engine, the rate of fuel feed being controlled by asuitable fuel control device, illustrated diagrammatically at 53, randthe high pressure delivery conduit 39 leads to the input sido of thesaid fuel control. The conduit 59 leading from the fue] control device58 represents a flow passage for metered fuel on the way to the burnerdischarge nozzles.

in order to regulate the pressure of the fuel in response to demands ofthe fuel control 53, a regulator valve 60 is provided and is connectedto a diaphragm 61, which forms a movable wall between a pair of meteredand unmetered fuel chambers 62 and 63. A spring 64 is located in chamber63 and normally urges the valve 60 to closed position. Chamber 64 isvented to metered fue] pressure by way of passage 65, while chamber 62is vented to pump discharge or unmetered fuel pressure by way of passage66: hence the differential across the diaphragm 6l is proportional tothe pressure drop across the fuel control unit, and any variation insaid drop will result in proportional repositioning of valve 60.

The passage 46, which receives pump control pressure fuel from theannular chamber or manifold 44, leads to the inlet side of a valve portor orifice 67, controlled by valve 60, and fuel flowing across this port67 passes into a passage 68, thence to chamber 69, across valve ports oropenings 7l), into passage 7l and thence to the low pressurc side of thepump l0, or the conduit 20. The valve ports 70 are formed in a hollowsliding dashpot valve member 72, secured to the adjacent side of adiaphragm 73, which forms a. movable wall between the chamber nl? and achamber 74, the latter being vented to leakage or ditlcrential fuelpressure by way of passage and passage 46. A calibrated restriction 75is located in passage 75. A spring 76 tends to move the valve 72 towardopen position in opposition to the pressure of the furl in chamber 74.The spring rate of spring 76 is preferably such as to produce asubstantially constant pressure drop across valve 60 during equilibriumoperation. 'l he purpose of valve 72 is to prevent too sudden in ow offluid past valve 60 in response to quick changes in position of saidvalve, and which sudden changes in ow would cause surging of thedelivery pressure. This action will be more fully explained in thefollowing description oiA operation.

Operation lt will be obvious that when shaft 4S is rotated, it in turneffects rotation of the wobble plate 47", and this in turn effectsreciprocation of the plungers i8 through the non-rotatable but rockablebearing ring 52, thrust plate S2 and Contact members 5:3. When used in afuel system as in the example illustrated. the drive shaft 48 will havea driving connection with the engine through the drive spline 4S.

@n the upper side of Figure l` the wobble plate 47 ha:V moved one of theplungers 18 to a substantially full discharge position. At the lowerside of said gure, one the plungers 18 is in its retracted position, atwhich point fuel is free to flow into the plunger chamber 23 from thepump chamber 1l by way of ports 24. The liow produced in the fueldischarge conduit 39, when the plungers 18 move to close the ports 24and expel fuel from chambers 23 outwardly through ports 34 and 36 intochamber 37, depends on the period of time the check .'z'ilvcs remainopen during the return or retraction stroke of the plungers, while thepressure generated in said com duit depends upon such period of time andthe restriction to flow due to the setting of the fuel control device58. For exan'iple, when the plungers lt; move back or are retracted,should the check valves 28 close instantly` all the fue] taken intochambers 23 will be low pressure fuel from the pump chamber ll, whereasshould the check vulves be held open during part of the retractingstroke of the plungers, then the chambers 23 will ll partly with highpressure fuel from chamber 37 and partly with low pressure fuel frompump chamber 1]. The period of time the check valves 28 remain open iscontrollable as a function of, or in relation to the drop between thepressure of the fuel in discharge passage 39, which may be consideredunmetered fuel pressure. and the pressure of the fuel in the passage 59,which may be considered as metered fuel pressure.

Let it be assumed that the pilot opens the throttle of the engine fuelcontrol device 58 and there is a momentary drop in pressure in passage39. This will immediately effect a reduction in the differential acrossthe check valves 28 tending to move the latter towards close position,so that when the plungers 18 retract, the said check valves willimmediately close and substantially all of the fuel expelled fromchambers 23 will come from the pump chamber 11. The differential acrossthe check valve is reduced due to the pressure in passage 39 beingcommunicated by way of passage 66 to diaphragm charnber 62, reducing thedifferential across the diaphragm 6l, so that the valve 60 will closethe port 67. Closure of the port 67 means that the pressure in back ofthe check valves 28, viz., the pressure in passage 46, annular chamber44 and check valve chambers 40, will immediately build up and reduceanti finally stop leakage of fuel past said valves.

When the metered fuel pressure attains the desired or selected value asdetermined by the setting of the pilots control lever, the pressure ofthe fuel in conduit 39 will have attained a value such that thedifferential across the diaphragm 6l will open valve 60 sufficiently topass enough fuel to the low pressure side of the pump by way of port 67,passage 68, chamber 69 and passage 71 to maintain an equilibriumcondition.

There may be times when the pump would tend to surge were it not for thevalve 72. To illustrate, let it be assumed that the system is operatingat some idle or intermediate setting of the fuel control 58 and thepilot suddenly opens the throttle for maximum delivery of fuel to theburner nozzles. Momentarily, there would be a drop in pressure inconduit 39 which would be communicated to diaphragm chamber 62, andsubstantially simultaneously there would be an increase in pressure inconduit S9 which would be communicated to diaphragm chamber 63. The fueldifferential across diaphragm 6l would quickly decrease and spring 64would tend to close valve 60. immediately pump delivery pressureincreases in conduit 39, however, and the fuel differential acrossdiaphragm 61 starts to build up to equilibrium; but before thiscondition occurs the valve 60 may have overshot, or moved beyondequilibrium. This would throw the valve 60 out of phase with theresponse of the pump, with resultant surging. However, the valve 72opens more or less gradually and prevents or damps sudden changes inflow across valve 60, bringing the response of the pump in harmony withthat of the valve 60. Another advantage is that the valve 60 may becontoured for less travel, thereby facilitating the use of a spring 64having a constant spring rate.

It will be seen that the fuel in chamber 37 not used to partially fillone set of plunger chambers 23 when the plungers 18 are retracted isutilized to fill another set of said chambers, viz., it is free to flowfrom chamber 37 back past any of the check valves 28, depending upon thedegree of closing movement of the latter. Thus the only displaced orexpelled fuel which is by-passed is that used for regulation, which isrelatively small and remains small even though much less fuel isconsumed by the cngine at high altitudes. By utilizing the differentialacross the check valve as a controlling medium in the manner heretoforedescribed, a relatively simple arrangement is pro-vided for varying thevolume delivery of a pump of the constant stroke reciprocating plungertype. Less power is required to drive a pump of the hereindisclosed typefor a given over-all range or average of pump discharge pressures thanis required for fixed displacement type pumps. This results from theassist to wobble plate rotation caused by the high pressure fuel returnthrough the check valve ports Whenever the fuel requirements are tessthan maximum volume discharge which reduces the effective torquerequired to drive the pump. As a consequence, there is less fluidtemperature rise across the pump,

Although only one embodiment of the invention has been illustrated anddescribed, the disclosure is amply sufficient to teach those skilled inthe art to adapt the invention to various installations other than thatshown.

I claim:

l. In a system for pressurizing fluid, a pump having a plurality ofpumping elements, means for imparting constant pumping strokes to saidelements, means providing individual pumping chambers in which saidelements move to expel fluid and from which said elements retract topermit inflow of fluid, said chambers having inlet ports for lowpressure till fluid and discharge ports through which fluid is expelled,check valves for ysaid discharge ports, an outlet for pressurized fluidcommon to said outlet ports, a device for variably controlling thepressure in said outlet, means resiliently urging said check valves toseated position, a portion formed on the seating side of said valves forsubjection to the fluid in said outlet, means permitting the passage offluid from said portion of the seating sides of said valves to theopposite sides thereof to establish a pump control fluid differentialpressure across said valves, a receiving chamber for fluid passed to theopposite sides of said check valves common to all of said valves, apassage through which fluid from said receiving chamber may flow to thelow pressure side of the pump, and means in said latter passage forvariably regulating the pressure in said receiving chamber as a functionof the pressure drop across said control device.

2. A system as claimed in claim l, wherein the means for variablyregulating the pressure in said receiving chamber comprising a regulatorvalve and means responsive to the pressure drop across said controldevice is provided for variably positioning said regulator valve.

3. A system as claimed in claim l, wherein the means for variablyregulating the pressure in said receiving chamber comprises a regulatorvalve and means responsive to the drop in pressure across said controldevice is provided for variably positioning said valve, and in additionthere is another valve responsive to the drop across said regulatorvalve for damping the response of the pump to the action of theregulator valve.

4. In a system for pressurizing fuel to an engine, a pump having aplurality of pumping elements, means for imparting constant pumpingstrokes to said elements, means providing individual pumping chambers inwhich said elements move to expel fuel and from which said elementsretract to prevent inflow of fuel, said chambers having inlet ports forlow pressure ll fuel and discharge ports through which fuel is expelled,means providing a chamber for expelled fuel common to said dischargeports, a passage for conducting fuel from said latter chamber to theengine, a fuel regulating device in said passage, check valvescontrolling said discharge ports, means permitting passage of a limitedquantity of fuel from the one side of said check valves to the oppositesides thereof to establish a pump control fuel differential pressureacross said valves, a receiving chamber for such last named fuel commonto all of said valves, a passage for conducting fuel from said receivingchamber to the low pressure side of' the pump, a valve for regulatingflow through said latter passage to thereby regulate the differentialacross said check valves, and means for variably positioning saidregulating valve in response to changes in the demands of the engine asdetermined by the rate of llc-w of fuel to the engine.

5. In a fuel supply system for an engine, a fuel pump having a pumpingchamber' provided with a fuel inlet port and a fuel discharge port, anoutlet conduit connected to said discharge port, a pumping member havinga substantially constant pumping stroke, a che-ck valve controlling saidfuel discharge port, means for establishing a pump control fueldifferential pressure across said check valve to control the seating ofsaid valve and regulate the flow from said outlet to said chamber, meansfor by-passing at least a portieri of the fuel utilized in creating suchdifferential pressure to a low pressure source, and means for variablyregulating the pressure of the by-passed fuel.

6. in `a system for pressurizing fuel to an engine, a pump having aplurality of reciprocating pumping plungers, a constant-angle wobbleplate for actuating said plungers, means for effecting rotation of saidwobble plate, means providing individual pumping chambers for saidplungers, said chambers having inlet ports for low pressure ll fue] anddischarge ports through which fuel is expelled, a passage for conductingfuel to the engine having an inlet common to said discharge ports, afuel regulating device in said passage, check valves controlling saiddischarge ports, means permitting leakage of fuel from one side of saidcheck valves to the opposite side thereof to establish a pump controlfuel differential pressure across said valves, a receiving chamber forleakage fuel common to all of said valves, a passage for conductingleakage fuel back to the low pressure side of the pump, a regulatingvalve in said passage, and means responsive to variations in the drop inpressure across said device for variably positioning said regulatingvalve.

7. ln a system for pressurizing fluids, a pump having a plurality ofpumping elements, means for imparting constant pumping strokes to saidelements, means providing individual pumping chambers into which saidelements move to expel uid and from which said elements retract topermit inow of fluid, said chambers having inlet ports for low pressurefill fluid and discharge ports through which iluid is expelled, meansproviding a chamber for expelled fluid common to said discharge ports,check valves controlling said discharge ports, means for continuouslysubjecting at least a portion of one side of said check valves to thefluid in said last mentioned chamber, means for subjecting a portion ofsaid one side of said check valves to the lluid in said pumpingchambers, means providing for leakage of fuel from said one side of saidcheck valves to the opposite side thereof to establish a pump controlfluid differential pressure across said valves, and means for variablyregulating the pressure exerted by said leakage fuel tending to seatsaid valves.

8. In a system for pressurizing fluids, a pump having a plurality ofpumping elements, means for imparting constant pumping strokes to saidelements, means providing individual pumping chambers into which saidelements move to expel fluid and from which said elements retract topermit inow of uid, said chambers having inlet ports for low pressurelill fluid and discharge ports through which iluid is expelled, meansproviding a chamber for expelled fluid common to said discharge ports, a7

pump discharge conduit leading from said latter chamber, means forcontinuously subjecting a portion of one side of said check valves tothe fluid in said last mentioned chamber, means for subjecting anotherportion of said one side of said check valves to the fluid in saidpumping chambers, means providing for the passage of fluid from one sideof said check valves to the opposite side thereof to establish a pumpcontrol uid differential pressure across said valves, a chamber for saidlast mentioned iluid common to all of said valves, and means forvariably controlling the pressure in said latter chamber as a functionof the pressure in said conduit.

9. In a system for pressurizing fluid, a pump having a plurality ofpumping elements, means for imparting constant pumping strokes to saidelements, means providing individual pumping chambers in which saidelements move to expel uid and from which said elements retract topermit inow of fluid, said chambers having inlet ports for low pressurefill fluid and discharge ports through which uid is expelled, checkvalves for said discharge ports, an outlet for pressurized fluid commonto said outlet ports, means continuously subjecting a portion of oneside of said check valves to the fluid in said outlet, means forsubjecting another portion of said one side of said check valves to thefluid in said pumping chambers, means resiliently urging said checkvalves to seated position, means permitting passage of uid from the rstmentioned portion of said one side of said valves to the opposite sidethereof to establish a pump control Huid differential pressure acrosssaid valves, a receiving chamber for fluid passed to the opposite sidesof the check valve common to all of said valves, a passage through whichfluid from said receiving chamber may ow to the low pressure side of thepump, and means for variably regulating the fluid pressure in saidlatter passage ns a function of the pressure in said outlet.

l0. A system as claimed in claim 9 wherein the means for regulating thepressure of fluid in said passage to the low pressure side of the pumpcomprises a regulator valve responsive to variations in pump dischargepressure.

ll. A system as claimed in claim 9 wherein the means for regulating thepressure of fluid in said passage to the low pressure side of the pumpcomprises a valve responsive to variations in pump discharge pressure,and means are provided for damping the action of said regulator valve.

References Cited in the tile of this patent UNITED STATES PATENTS1,010,206 Wainwright Nov. 28, 1911 1,690,097 Ackermann Nov. 6, 19282,018,119 Brouse Oct. 22, 1935 2,268,000 Treer Dec. 30, 1941` 2,381,528Trich Aug. 7, 1945 2,395,964 Fodor Mar. 5, 1.946 2,433,220 Huber Dec.23, 1947 2,506,162 Metzgar May 2, 1950 2,549,711 Ruben Apr. 17, 19512,575,677 Neu Nov. 20, 1951 2,582,535 Drouot Jan. 15, 1952 2,636,438Roustan Apr. 28, 1953 2,682,227 Burris June 29, 1954 FOREIGN PATENTS48,535 Denmark Mar. 9, 1934

